Sealing alloy

ABSTRACT

A GLASS SEALING ALLOY COMPRISING, AS EXPRESSED IN PERCENT A WEIGHT, THE FOLLOWING MAJOR CONSTITUENTS: PERCENT NICKEL 5.5-20.0 COBALT 42.5-57.0 CHROMIUM 5.0-6.5 IRON BALANCE THE SUM OF THE NICKEL AND COBALT CONSTITUENTS FALLING WITHIN THE RANGE 62.0%-63.0%.

ABSTRACT OF THE DISCLOSURE A glass sealing alloy comprising, asexpressed in percent by weight, the following major constituents:

Percent Nickel 5.5-20.0 Cobalt 42.5-57.0 Chromium 5.0-6.5 Iron Balancethe sum of the nickel and cobalt constituents falling with in the range62.0%63.0%.

BACKGROUND OF THE INVENTION In order to provide a satisfactory hermeticseal between the glass envelope of an electron device and electricalleads or pins, a sealing alloy known as 52 alloys is conventionallyused. This is an essentially binary alloy containing 52% of weight ofnickel, balance iron. However, seals of this type can exhibit a tendencyto leak due to incomplete or insuflicient adherence of the metal oxidewhereby the hermeticity is destroyed. The exposed surfaces of thissealing alloy have poor corrosion resistance in most environments.

I have discovered that a quaternary alloy having nickel, iron, cobaltand chromium components can be used to overcome this difliculty. Moreparticularly, this new alloy is characterized by the ability to formtight, adherent hermetic bonds in glass to metal seals, and alsoexhibits the same thermal expansion properties as 52 alloy. Moreover, myalloy exhibits enhanced corrosion resistance in most environments. As aresult, my alloy can be substituted for 52 alloy in sealing applicationswith the advantages indicated.

SUMMARY OF THE INVENTION In accordance with the principles of myinvention, my alloy comprises the following major constituents asexpressed in percent by weight:

Percent Nickel 5.5-20-.0

Cobalt 42.5-57.0

the sum of the nickel and cobalt constituents falling within the range62.0%63.0%;

Chromium Iron 5.0-6.5 Balance The alloy contains up to 1% of certainminor constituents including;

Manganese -0.5 Silicon 0-0.4

United States Patent 0 M 3,726,671 Patented Apr. 10, 1973 DETAILEDDESCRIPTION OF PREFERRED EMBODIMENTS One typical alloy composition inaccordance with my invention is as follows:

The thermal coefficient of expansion of this composition, from 25 C. to450 C., was found to be 9.79 p.p.m./ C. The thermal coeflicient ofexpansion of 52 alloy is essentially the same. However, my alloy can beused to provide enhanced adherence and hermetic bonding as previouslyindicated. My alloy forms a stable, single phase, solid solution.Providing that the major constituents of my alloy are held within theranges recited above, the expansion coefiicient will be held within therange 8 p.p.m./ C. to 11 p.p.m./ C., and the alloy will not undergo anyallotropic transformations. Moreover my alloy is much less susceptibleto corrosion attack.

As a specific example, for 15 minutes in 20% nitric acid at 180 F.,using samples having equivalent surface areas, the 52 alloy showed 17.3%weight loss as compared to only .02% weight loss for my alloy.Advantages can also be shown in other corrosive environments.

The minor constituents should be held within the ranges indicated below:

Chromium is added to enhance the adherence of the oxide formed in makingglass to metal seals. Below 5% chromium, there is little enhancement.Additions of chromium in excess of 6.5% produces no further enhancement.In addition, these chromium additions have a passivating elfect incomparison to 52 alloy whereby my alloy is more corrosion resistant.

Unless the sum of the nickel and cobalt constituents of my alloy is heldwithin the range 62.0%-63.0%, the curie temperature and relatedinflection temperature will not be maintained at the same values as inthe 52 alloy, and the resultant thermal coefficient of expansion willfall outside the desired range.

When the sum of nickel and cobalt is held between 62% and 63 the lowerlimit of Ni is 5.5%. When the nickel content falls below this value, thealloy is likely to be a two phase structure as opposed to a single phasestructure. The expansion behavior of a two phase structure can beunstable and unpredictable.

The upper limit of the nickel content is 20%. When nickel is substitutedfor cobalt and the sum of these two constituents is held within therange 62.0%-63.0%, nickel additions in excess of 20% produce expansioncoefficient which are too high:

My alloy can be produced by the same procedures as required for 52alloy. No special precautions are necessary, but the alloy should beclean and relatively defect free.

While I have described my invention with particular reference topreferred embodiments, my protection is limited only by the terms of theclaims which follow.

What is claimed is:

1. An alloy, as expressed in percent by Weight, consisting essentiallyof:

3 the sum of the nickel and cobalt falling within the range 62.0%63.0%.'

Percent Cromium 5.0-6.5 Silicon Balance 2. An alloy as set forth inclaim 1 further including:

Percent Manganese 0-0.5 Silicon 0-0.4 m

3. An alloy as set forth in claim 2 containing:

Percent Nickel 14 Cobalt 48.5 15 Chromium 6.0

Silicon 0.1 Managanese 0.35

References Cited UNITED STATES PATENTS 1/ 1932 Elmen 75-123 K 6/1936Halliwell 75123K X 12/1936 Scott 75170 X FOREIGN PATENTS 10/1931 GreatBritain 75123 K US. Cl. X.R.

